Major changes occur in carbohydrate expression during the onset and progression of cancer. These changes include both loss of normal cell surface carbohydrates (e.g., ABO blood group antigens) as well as greater levels of expression of carbohydrate structures that normally have lesser and/or restricted expression levels in most healthy adults (called tumor-associated carbohydrate antigens). In many cases, these tumor associated antigens are found on cell surfaces and/or secreted proteins, making them accessible for binding and detection. As a result, carbohydrate antigens have become important molecular targets for cancer diagnostics and therapeutics. One example is the Tn antigen; a carbohydrate composed of a GalNAc residue alpha linked to either a serine or threonine residue of a polypeptide/protein.
Studies have examined the expression of the Tn antigen in cervical and other cancers, and evaluated its utility as a prognostic marker; however, the results remain a subject of considerable debate. These studies have relied on immunohistochemical staining or Western blotting with Tn binding antibodies and/or lectins for the detection of the Tn antigen.